Demonstration of a metastable argon laser of 10†W by transverse pumping.

Optically pumped metastable rare gas lasers have been extensively investigated as promising high-energy lasers. These systems employ discharge-excited metastable inert gases as the lasing medium. Following optical pumping, a buffer gas, typically helium, is introduced to facilitate a collisional population transfer to the p2[1/2]1 level, thereby establishing population inversion. To date, laser outputs in the watt level have been demonstrated. However, further power scaling crucially depends on the ability to stably generate high metastable densities at elevated pressures approaching atmospheric conditions. In this Letter, we report a pulsed discharge technique based on a peaking capacitor rapid discharge circuit, which is capable of producing metastable particle densities exceeding 1014 cm-3 at pressures up to 900 mbar. By employing this discharge approach in conjunction with transverse optical pumping, we have realized a maximum output power of 12.5 W from a semiconductor-pumped metastable argon laser system.

Production of high-density metastable argon atoms with periodic fast pulsed DC discharge.

Optically pumped metastable rare gas laser (OPRGL), as a potential high-energy laser has attracted much attention. During extensive research on OPRGL, the realization of volume discharge with high-metastable density has always been a priority and is essential to the efficient lasing of OPRGL. A large-volume plasma of He/Ar with high metastable density at atmospheric pressure can be generated by applying peaking capacitors near the electrodes. In this article, 0.8 cm3 of He/Ar plasma at a pressure of 900 mBar, with a peak value of metastable argon density higher than 1014 cm-3 was realized. The metastable density was measured by absorption spectroscopy based on the absorption bandwidths acquired at a pressure range of 400-900 mbar where a probe beam at a weak line with wavelength 772.38 nm was applied. Furthermore, the high metastable density was verified by the laterally-observed laser-induced fluorescence, as well as the laser oscillation of 100 mW under a longitudinal pumping with a short gain length of 8 mm.

Time-dependent simulations of a CW pumped, pulsed DC discharge Ar metastable laser system.

Optically pumped rare gas lasers have the potential for scaling to output powers above the kW level. In these devices, electrical discharges through He/Rg mixtures (Rg = Ne, Ar, Kr and Xe) are used to generate metastable Rg atoms in the 1s5 state. Optical pumping to the 2p9 level, followed by collisional relaxation to 2p10, is then used to produce lasing on the 2p10-1s5 transition. Several computational models have been developed to analyze CW systems using steady-state approximations for the discharge excitation, optical pumping and lasing processes. However, recent experiments show that repetitively pulsed discharges have advantages for producing larger volume, high-pressure discharges. Here we present dynamic simulations of a CW laser that uses pulsed-discharge production of Ar metastables. Time-dependent equations are solved for both the discharge and lasing process. Two models are investigated. The first considers the conditions within the lasing medium to be spatially uniform (zero-dimensional model). The second allows for spatial variations along the lasing axis (one-dimensional model). The models were evaluated by simulating the performance characteristics of an experimentally demonstrated system that provides time-averaged output energies in the range of 3-4 W. Time-dependent species densities, laser power and longitudinal spatial distributions are presented.

Perfect narrow band absorber for sensing applications.

We design and numerically investigate a perfect narrow band absorber based on a metal-metal-dielectric-metal structure which consists of periodic metallic nanoribbon arrays. The absorber presents an ultra narrow absorption band of 1.11 nm with a nearly perfect absorption of over 99.9% in the infrared region. For oblique incidence, the absorber shows an absorption more than 95% for a wide range of incident angles from 0 to 50°. Structure parameters to the influence of the performance are investigated. The structure shows high sensing performance with a high sensitivity of 1170 nm/RIU and a large figure of merit of 1054. The proposed structure has great potential as a biosensor.

Parabolic cell for low-background Raman analysis of gas samples.

A compact Raman system constructed by a parabolic sample cell and an imaging spectrograph, which has good capability for enhancing a Raman signal and compressing a continuous background, has been put forward. In the Raman spectra of ambient air acquired by this system, the signal level of N2 was enhanced up to 14 times compared with free space, and the related signal to background ratio was increased nearly to 96. With an integration time of 10 s, the rotational fine structure of O2 and N2 were clearly recognized. Besides, a standard analytic gas mixture consisting of H2, CO2, and CO was also tested, and the 3σ LODs of 68 ppm for H2, 54 ppm for CO2 and 116 ppm for CO were obtained.

Characteristics of laser induced discharge tin plasma and its extreme ultraviolet radiation.

In this paper, a CO2 laser induced discharge plasma extreme ultraviolet (EUV) source experimental device was established. The optical emission spectroscopy was used to diagnose the characteristics of the plasma, and the evolution of electron temperature and electron density with time was obtained. The influence of discharge voltage on plasma parameters was analyzed and discussed. The EUV radiation characteristics of the plasma were investigated by self-made grazing incidence EUV spectrometer. The EUV radiation intensity and conversion efficiency were discussed.